Not applicable.
The invention provides isolated nucleic acid and amino acid sequences of taste cell specific G-protein coupled receptors, antibodies to such receptors, methods of detecting such nucleic acids and receptors, and methods of screening for modulators of taste cell specific G-protein coupled receptors.
Taste transduction is one of the most sophisticated forms of chemotransduction in animals (see, e.g., Margolskee, BioEssays 15:645-650 (1993); Avenet and Lindemann, J. Membrane Biol. 112:1-8 (1989)). Gustatory signaling is found throughout the animal kingdom, from simple metazoans to the most complex of vertebrates; its main purpose is to provide a reliable signaling response to non-volatile ligands. Each of these modalities is though to be mediated by distinct signaling pathways mediated by receptors or channels, leading to receptor cell depolarization, generation of a receptor or action potential, and release of neurotransmitter at gustatory afferent neuron synapses (see, e.g., Roper, Ann. Rev. Neurosci. 12:329-353 (1989)).
Mammals are believed to have five basic taste modalities: sweet, bitter, sour, salty, and umami (the taste of monosodium glutamate) (see, e.g. Kawamura and Kare, Introduction to Umami: A Basic Taste (1987); Kinnamon and Cummings, Ann. Rev. Physiol. 54:715-731(1992); Lindemann, Physiol. Rev. 76:718-766 (1996); Stewart et al., Am. J. Physiol. 272:1-26 (1997)). Extensive psychophysical studies in humans have reported that different regions of the tongue display different gustatory preferences (see, e.g., Hoffmann, Menchen. Arch. Path. Anat. Physiol. 62:516-530 (1875); Bradley et al., Anatomical Record 212: 246-249 (1985); Miller and Reedy, Physiol. Behav. 47:1213-1219 (1990)). Also, numerous physiological studies in animals have shown that taste receptor cells may selectively respond to different tastants (see, e.g., Akabas et al., Science 242:1047-1050 (1988); Gilbertson et al., J. Gen. Physiol. 100:803-24 (1992); Bernhardt et al., J. Physiol. 490:325-336 (1996); Cummings et al., J. Neurophysiol. 75:1256-1263 (1996)).
In mammals, taste receptor cells are assembled into taste buds that are distributed into different papillae in the tongue epithelium. Circumvallate papillae, found at the very back of the tongue, contain hundreds (mice) to thousands (human) of taste buds and are particularly sensitive to bitter substances. Foliate papillae, localized to the posterior lateral edge of the tongue, contain dozens to hundreds of taste buds and are particularly sensitive to sour and bitter substances. Fungiform papillae containing a single or a few taste buds are at the front of the tongue and are thought to mediate much of the sweet taste modality.
Each taste bud, depending on the species, contains 50-150 cells, including precursor cells, support cells, and taste receptor cells (see, e.g., Lindemann, Physiol. Rev. 76:718-766 (1996)). Receptor cells are innervated at their base by afferent nerve endings that transmit information to the taste centers of the cortex through synapses in the brain stem and thalamus. Elucidating the mechanisms of taste cell signaling and information processing is critical for understanding the function, regulation, and xe2x80x9cperceptionxe2x80x9d of the sense of taste.
Although much is known about the psychophysics and physiology of taste cell function, very little is known about the molecules and pathways that mediate these sensory signaling responses (reviewed by Gilbertson, Current Opin. Neurobiol. 3:532-539 (1993)). Electrophysiological studies suggest that sour and salty tastants modulate taste cell function by direct entry of H+ and Na+ ions through specialized membrane channels on the apical surface of the cell. In the case of sour compounds, taste cell depolarization is hypothesized to result from H+ blockage of K+ channels (see, e.g., Kinnamon et al., Proc. Nat""l Acad. Sci. USA 85: 7023-7027 (1988)) or activation of pH-sensitive channels (see, e.g., Gilbertson et al., J. Gen. Physiol. 100:803-24 (1992)); salt transduction may be partly mediated by the entry of Na+ via amiloride-sensitive Na+ channels (see, e.g., Heck et al., Science 223:403-405 (1984); Brand et al., Brain Res. 207-214 (1985); Avenet et al., Nature 331: 351-354 (1988)).
Sweet, bitter, and umami transduction are believed to be mediated by G-protein-coupled receptor (GPCR) signaling pathways (see, e.g., Striem et al., Biochem. J. 260:121-126 (1989); Chaudhari et al., J. Neuros. 16:3817-3826 (1996); Wong et al., Nature 381: 796-800 (1996)). Confusingly, there are almost as many models of signaling pathways for sweet and bitter transduction as there are effector enzymes for GPCR cascades (e.g., G protein subunits, cGMP phosphodiesterase, phospholipase C, adenylate cyclase; see, e.g., Kinnamon and Margolskee, Curr. Opin. Neurobiol. 6:506-513 (1996)). However, little is known about the specific membrane receptors involved in taste transduction, or many of the individual intracellular signaling molecules activated by the individual taste transduction pathways. Identification of such molecules is important given the numerous pharmacological and food industry applications for bitter antagonists, sweet agonists, and other modulators of taste.
One taste-cell specific G protein that has been identified is called Gustducin (McLaughin et al., Nature 357:563-569 (1992)). This protein is proposed to be involved in the detection of certain bitter and sweet tastes (Wong et al., Nature 381:796-800 (1996)), and is expressed in a significant subset of cells from all types of taste papillae (McLaughin et al., Nature 357:563-569 (1992)).
Recently, two novel GPCRs were identified and found to be specifically expressed in taste cells. While these receptor proteins, called TRI and TR2, appear to be directly involved in taste reception (Hoon et al., Cell 96:541-551 (1999)), they are only expressed in a fraction of mammalian taste receptor cells. For example, neither of the genes are extensively expressed in Gustducin-expressing cells. Thus, it is clear that additional taste-involved GPCRs remain to be discovered.
Genetic studies in mammals have identified numerous loci that are involved in the detection of taste. For example, psychophysical tasting studies have shown that humans can be categorized as tasters, non-tasters, and super-tasters for the bitter substance PROP (6-n-propylthiouracil), and that PROP tasting may be conferred by a dominant allele, with non-tasters having two recessive alleles and tasters having at least one dominant allele (see Bartoshuk et al., Physiol Behav 56(6):1165-71; 58:203-204 (1994)). Recently, a locus involved in PROP tasting has been mapped to human interval 5p15 (Reed et al., Am. J. Hum. Genet., 64(5):1478-80 (1999)). The PROP tasting gene present at the 5p 15 locus has yet to be described, however.
In addition, a number of genes involved in taste have been mapped in mice. For example, a cluster of genes involved in bitter-taste detection has been mapped to a region of chromosome 6 in mice (Lush et al., Genet Res. 66:167-174 (1995)).
The identification and isolation of novel taste receptors and taste signaling molecules would allow for new methods of pharmacological and genetic modulation of taste transduction pathways. For example, the availability of receptor and channel molecules would permit the screening for high affinity agonists, antagonists, inverse agonists, and modulators of taste cell activity. Such taste modulating compounds would be useful in the pharmaceutical and food industries to customize taste. In addition, such taste cell specific molecules can serve as invaluable tools in the generation of taste topographic maps that elucidate the relationship between the taste cells of the tongue and taste sensory neurons leading to taste centers in the brain.
The present invention thus provides novel nucleic acids encoding a family of taste-cell specific G-protein coupled receptors. These nucleic acids and the polypeptides that they encode are referred to as the xe2x80x9cSf,xe2x80x9d or xe2x80x9cGRxe2x80x9d family of G-protein coupled taste receptors. This novel family of GPCRs includes components of the taste transduction pathway. In particular, members of this family are involved in the detection of bitter tastes.
In one aspect, the present invention provides a method for identifying a compound that modulates taste signaling in taste cells, the method comprising the steps of: (i) contacting the compound with a taste transduction G-protein coupled receptor polypeptide, wherein the polypeptide is expressed in a taste cell, the polypeptide comprising greater than about 60% amino acid sequence identity to a sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49, SEQ ID NO:51, SEQ ID NO:53, SEQ ID NO:55, SEQ ID NO:56, SEQ ID NO:58, SEQ ID NO:60, SEQ ID NO:62, SEQ ID NO:64, SEQ ID NO:66, SEQ ID NO:68, SEQ ID NO:70, SEQ ID NO:72, SEQ ID NO:74, SEQ ID NO:76, SEQ ID NO:78, and SEQ ID NO:80; and (ii) determining the functional effect of the compound upon the polypeptide.
In another aspect, the present invention provides a method for identifying a compound that modulates taste signaling in taste cells, the method comprising the steps of: (i) contacting the compound with a polypeptide comprising an extracellular domain of a taste transduction G-protein coupled receptor, wherein the receptor is expressed in a taste cell, the extracellular domain comprising greater than about 60% amino acid sequence identity to the extracellular domain of a polypeptide comprising a sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49, SEQ ID NO:51, SEQ ID NO:53, SEQ ID NO:55, SEQ ID NO:56, SEQ ID NO:58, SEQ ID NO:60, SEQ ID NO:62, SEQ ID NO:64, SEQ ID NO:66, SEQ ID NO:68, SEQ ID NO:70, SEQ ID NO:72, SEQ ID NO:74, SEQ ID NO:76, SEQ ID NO:78, and SEQ ID NO:80; and (ii) determining the functional effect of the compound upon the extracellular domain.
In another aspect, the present invention provides a method for identifying a compound that modulates taste signaling in taste cells, the method comprising the steps of: (i) contacting the compound with a taste transduction G-protein coupled receptor polypeptide comprising either: (a) a sequence comprising at least about 50% amino acid identity to a sequence selected from the group consisting of SEQ ID NO:82, SEQ ID NO:83, SEQ ID NO:84, SEQ ID NO:85, SEQ ID NO:86, and SEQ ID NO:87; or (b) a sequence selected from the group consisting of SEQ ID NO:88, SEQ ID NO:89, SEQ ID NO:90, and SEQ ID NO:91; and (ii) determining the functional effect of the compound upon the polypeptide.
In one embodiment, the polypeptide has G-protein coupled receptor activity. In another embodiment, the functional effect of the compound upon the polypeptide is determined by measuring changes in intracellular cAMP, cGMP, IP3, or Ca2+. In another embodiment, the functional effect is a chemical effect. In another embodiment, the functional effect is a physical effect. In another embodiment, the functional effect is determined by measuring binding of the compound to an extracellular domain of the polypeptide. In another embodiment, the functional effect is determined by measuring radiolabeled GTP binding to the polypeptide. In another embodiment, the functional effect is measured by determining changes in the electrical activity of cells expressing the polypeptides.
In another embodiment, the polypeptide or parts thereof is recombinant. In another embodiment, the polypeptide comprises an extracellular domain that is covalently linked to a heterologous polypeptide, forming a chimeric polypeptide. In another embodiment, the polypeptide is linked to a solid phase, either covalently or non-covalently.
In another embodiment, the polypeptide is from a rat, a mouse, or a human. In another embodiment, the polypeptide is expressed in a cell or a cell membrane. In another embodiment, the cell is a eukaryotic cell. In another embodiment, the polypeptide comprises an amino acid sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49, SEQ ID NO:51, SEQ ID NO:53, SEQ ID NO:55, SEQ ID NO:56, SEQ ID NO:58, SEQ ID NO:60, SEQ ID NO:62, SEQ ID NO:64, SEQ ID NO:66, SEQ ID NO:68, SEQ ID NO:70, SEQ ID NO:72, SEQ ID NO:74, SEQ ID NO:76, SEQ ID NO:78, and SEQ ID NO:80.
In one aspect, the present invention provides an isolated nucleic acid encoding a taste transduction G-protein coupled receptor, wherein the receptor is expressed in a taste cell, the receptor comprising greater than about 60% amino acid sequence identity to a sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33.
In another aspect, the present invention provides an isolated nucleic acid encoding a taste transduction G-protein coupled receptor, wherein the nucleic acid specifically hybridizes under highly stringent conditions to a nucleic acid having a nucleotide sequence selected from the group consisting of SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NOS:8 and 92, SEQ ID NO:10; SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:28, SEQ ID NO:30, SEQ ID NO:32, and SEQ ID NO:34, but not to a nucleic acid having a nucleotide sequence selected from the group consisting of SEQ ID NO:36, SEQ ID NO:38, SEQ ID NO:40, SEQ ID NO:42, SEQ ID NO:44, SEQ ID NO:46; SEQ ID NO:48, SEQ ID NO:50, SEQ ID NO:52, SEQ ID NO:54, SEQ ID NO:57, SEQ ID NO:59, SEQ ID NO:61, SEQ ID NO:63, SEQ ID NO:65, SEQ ID NO:67, SEQ ID NO:69, SEQ ID NO:71, SEQ ID NO:73, SEQ ID NO:75, SEQ ID NO:77, SEQ ID NO:79, and SEQ ID NO:81.
In another aspect, the present invention provides an isolated nucleic acid encoding a taste transduction G-protein coupled receptor, the receptor comprising greater than about 60% amino acid identity to a polypeptide having an amino acid sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33, wherein the nucleic acid selectively hybridizes under moderately stringent hybridization conditions to a nucleotide sequence having a nucleotide sequence selected from the group consisting of SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NOS:8 and 92, SEQ ID NO:10; SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:28, SEQ ID NO:30, SEQ ID NO:32, and SEQ ID NO:34 but not to a nucleic acid having a nucleotide sequence selected from the group consisting of SEQ ID NO:36, SEQ ID NO:38, SEQ ID NO:40, SEQ ID NO:42, SEQ ID NO:44, SEQ ID NO:46; SEQ ID NO:48, SEQ ID NO:50, SEQ ID NO:52, SEQ ID NO:54, SEQ ID NO:57, SEQ ID NO:59, SEQ ID NO:61, SEQ ID NO:63, SEQ ID NO:65, SEQ ID NO:67, SEQ ID NO:69, SEQ ID NO:71, SEQ ID NO:73, SEQ ID NO:75, SEQ ID NO:77, SEQ ID NO:79, and SEQ ID NO:81.
In another aspect, the present invention provides an isolated nucleic acid encoding an extracellular domain of a taste transduction G-protein coupled receptor, wherein the receptor is expressed in a taste cell, the extracellular domain having greater than about 60% amino acid sequence identity to the extracellular domain of a polypeptide comprising an amino acid sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33.
In one embodiment, the nucleic acid encodes a receptor that specifically binds to polyclonal antibodies generated against a polypeptide having an amino acid sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33, but not to polyclonal antibodies generated against a polypeptide having an amino acid sequence selected from the group consisting of SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49, SEQ ID NO:51, SEQ ID NO:53, SEQ ID NO:55, SEQ ID NO:56, SEQ ID NO:58, SEQ ID NO:60, SEQ ID NO:62, SEQ ID NO:64, SEQ ID NO:66, SEQ ID NO:68, SEQ ID NO:70, SEQ ID NO:72, SEQ ID NO:74, SEQ ID NO:76, SEQ ID NO:78, and SEQ ID NO:80.
In another embodiment, the nucleic acid encodes a receptor comprising an amino acid sequence of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33.
In another embodiment, the nucleic acid comprises a nucleotide sequence selected from the group consisting of SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NOS:8 and 92, SEQ ID NO:10; SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:28, SEQ ID NO:30, SEQ ID NO:32, and SEQ ID NO:34.
In another embodiment, the nucleic acid encodes a receptor that has G-protein coupled receptor activity. In another embodiment, the nucleic acid is from a rat or a mouse. In another embodiment, the nucleic acid is amplified by primers that selectively hybridize under stringent hybridization conditions to the same sequence as degenerate primer sets encoding amino acid sequences selected from the group consisting of:
In one embodiment, the nucleic acid encodes the extracellular domain linked to a heterologous polypeptide, forming a chimeric polypeptide. In another embodiment, the nucleic acid encodes the extracellular domain of a polypeptide comprising an amino acid sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:1, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33.
In another aspect, the present invention provides an isolated taste transduction G-protein coupled receptor, wherein the receptor is expressed in a taste cell, the receptor comprising greater than about 60% amino acid sequence identity to a sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33.
In one embodiment, the receptor specifically binds to polyclonal antibodies generated against a polypeptide having an amino acid sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33, but not to polyclonal antibodies generated against a polypeptide having an amino acid sequence selected from the group consisting of SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49, SEQ ID NO:51, SEQ ID NO:53, SEQ ID NO:55, SEQ ID NO:56, SEQ ID NO:58, SEQ ID NO:60, SEQ ID NO:62, SEQ ID NO:64, SEQ ID NO:66, SEQ ID NO:68, SEQ ID NO:70, SEQ ID NO:72, SEQ ID NO:74, SEQ ID NO:76, SEQ ID NO:78, and SEQ ID NO:80. In another embodiment, the receptor has G-protein coupled receptor activity. In another embodiment, the receptor has an amino acid sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33. In another embodiment, the receptor is from a rat or a mouse.
In one aspect, the present invention provides an isolated polypeptide comprising an extracellular domain of a taste transduction G-protein coupled receptor, wherein the receptor is expressed in a taste cell, the extracellular domain comprising greater than about 60% amino acid sequence identity to the extracellular domain of a polypeptide comprising an amino acid sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33.
In one embodiment, the polypeptide encodes the extracellular domain of a polypeptide comprising an amino acid sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33. In another embodiment, the extracellular domain is covalently linked to a heterologous polypeptide, forming a chimeric polypeptide.
In one aspect, the present invention provides an antibody that selectively binds to the receptor comprising greater than about 60% amino acid sequence identity to a sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33.
In another aspect, the present invention provides an expression vector comprising a nucleic acid encoding a taste transduction G-protein coupled receptor, wherein the receptor is expressed in a taste cell, the receptor comprising greater than about 60% amino acid sequence identity to a sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, and SEQ ID NO:33.
In another aspect, the present invention provides a host cell transfected with the expression vector.